Cooperativity as quantification and optimization paradigm for nuclear receptor modulators.

Nuclear Receptors (NRs) are highly relevant drug targets, for which small molecule modulation goes beyond a simple ligand/receptor interaction. NR-ligands modulate Protein-Protein Interactions (PPIs) with coregulator proteins. Here we bring forward a cooperativity mechanism for small molecule modulation of NR PPIs, using the Peroxisome Proliferator Activated Receptor γ (PPARγ), which describes NR-ligands as allosteric molecular glues. The cooperativity framework uses a thermodynamic model based on three-body binding events, to dissect and quantify reciprocal effects of NR-coregulator binding ( K I D ) and NR-ligand binding ( K II D ), jointly recapitulated in the cooperativity factor ( α ) for each specific ternary ligand·NR·coregulator complex formation. These fundamental thermodynamic parameters allow for a conceptually new way of thinking about structure-activity-relationships for NR-ligands and can steer NR modulator discovery and optimization via a completely novel approach.